The 1858 Russian Empire Revision List from Buki still exists. And it turns out that there are multiple Zubaty families recorded in that census. Unfortunately, even the head of the Zoupcoff family in Pittsburgh, Meyer, wasn't born until 1872. However, I know from Meyer's tombstone that his father's name was Michel--and Michel would have been born by 1858.

Of all the 14 1858-recorded Zubaty families, there's one strong potential match:

1858 Buki Revision List; Zubaty Family (#42)--males

1858 Buki Revision List; Zubaty Family (#42)--females

Males

Itsko (son of Shevel) Zubaty, aged 41

Itzko's sons:

Michel, aged 14

Nochum, aged 7

Itzko's brother Srul (son of Shevel), aged 32

Srul's sons:

Shevel, aged 11

Yolik, aged 4

Females

Itzko's wife Etya, aged 38

Itzko's daughter Leya, aged 9

Srul's wife Chana, aged 31

Srul's daughters:

Rochela, aged 10

Chaya, aged 3

Shevel is a Russian version of Shaul, also the first name of my 3rd great grandfather Shaul Dov Zubkis/Supkoff. Could Shaul Dov and Shevel been named for a common ancestor? Also, Michel is about the right age to be Meyer Zoupcoff's father. Could this be the connection?

At this point I've raised more questions than I've answered. But hopefully all of these puzzle pieces will eventually come together to form a fuller picture of these families' relationship.